The correct option is Docker container action because it packages the action and its dependencies inside a container so it will always run in the same Alpine Linux 3.18 environment with the pinned system libraries and bespoke tools on any runner.

A Docker container action lets you define a Dockerfile that starts from alpine 3.18 and installs your custom CLI tools and pins library versions. GitHub builds or pulls that image and executes the action inside it which isolates execution from the host runner and guarantees the same operating system and system libraries every time.

Self-hosted runner is a runner choice rather than an action type and it ties execution to specific machines that you manage. It does not package the action’s environment so it cannot ensure the same Alpine 3.18 image and pinned libraries across any runner.

A JavaScript action runs on the host runner’s operating system using Node which means it inherits whatever system libraries and distribution the runner provides. It cannot enforce Alpine 3.18 or pinned system libraries by itself.

A Composite action only orchestrates other steps and runs in the surrounding job environment. By itself it cannot define or guarantee a specific operating system or toolchain.

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